1. Field of the Invention
Exemplary aspects of the present invention relate to a fixing device and an image forming apparatus, and more particularly, to a fixing device for fixing a toner image on a recording medium and an image forming apparatus incorporating the fixing device.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of a photoconductor; an optical writer emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a development device supplies toner to the electrostatic latent image formed on the photoconductor to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the photoconductor onto a recording medium or is indirectly transferred from the photoconductor onto a recording medium via an intermediate transfer belt; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
Such fixing device is requested to shorten a first print time taken to output the recording medium bearing the toner image onto the outside of the image forming apparatus after the image forming apparatus receives a print job. Additionally, the fixing device is requested to reduce power consumption.
To address these requests, the fixing device may employ a thin endless belt having a decreased thermal capacity and therefore heated quickly by a heater. For example, a pressing roller is pressed against a nip formation assembly disposed inside a loop formed by the endless belt to form a fixing nip between the pressing roller and the endless belt. The heater disposed inside the loop formed by the endless belt heats the endless belt throughout the width in the axial direction thereof. As the pressing roller and the endless belt rotate and convey the recording medium bearing the toner image through the fixing nip, the endless belt and the pressing roller apply heat and pressure to the recording medium, thus fixing the toner image on the recording medium. Since the heater heats the endless belt directly, the endless belt is heated to a predetermined fixing temperature quickly, thus meeting the above-described requests of shortening the first print time and reducing power consumption.
As the recording medium bearing the toner image passes through the fixing nip, it travels over a center of the endless belt in the axial direction thereof. Accordingly, both lateral ends of the endless belt in the axial direction thereof where the recording medium does not travel are subject to damage, for example, thermal damage and mechanical damage.
For example, as the recording medium travels over the center of the endless belt in the axial direction thereof, it draws heat from the center of the endless belt. Conversely, at both lateral ends of the endless belt in the axial direction thereof where the recording medium does not travel, heat is not drawn therefrom to the recording medium. Accordingly, both lateral ends of the endless belt may overheat, resulting in thermal damage of the endless belt.
On the other hand, as the recording medium is discharged from the fixing nip, it may adhere to the endless belt and thereby may not be discharged from the fixing device smoothly. To address this problem, a separator may be disposed opposite the outer circumferential surface of the endless belt at each lateral end of the endless belt in the axial direction thereof. As the recording medium is discharged from the fixing nip, the separator comes into contact with the leading edge of the recording medium, separating the recording medium from the endless belt. However, if the recording medium is accidentally jammed between the endless belt and the separator, a user may pull the jammed recording medium upward to remove it from between the endless belt and the separator. Accordingly, the recording medium pulled upward lifts and spaces the separator apart from the endless belt. However, after the jammed recording medium is removed, the separator no longer lifted by the recording medium may fall and strike the endless belt by resilience of a spring anchored to the separator, thus mechanically deforming or damaging both lateral ends of the endless belt in the axial direction thereof.